1,848 research outputs found
Detecting the Transition From Pop III to Pop II Stars
We discuss the cosmological significance of the transition from the Pop III
to Pop II mode of star formation in the early universe, and when and how it may
occur in primordial galaxies. Observations that could detect this transition
include those of element abundances in metal-poor Galactic halo stars, and of
the helium reionization and associated heating of the intergalactic medium. We
suggest that gamma-ray bursts may be a better probe of the end of the
first-stars epoch than of Pop III stars.Comment: 10 pages, 3 figures; to appear in New Astronomy Reviews as
proceedings of "First Light and Reionization Workshop", eds. A. Cooray & E.
Barton, Irvine, CA, May 19-21, 200
Formation Of The First Galaxies
The emergence of the first stars and galaxies ended the cosmic dark ages, thus fundamentally transforming the simple initial state of the universe into one of ever increasing complexity. We will review the basic physics governing the formation of the first galaxies. Their properties sensitively depend on the feedback exerted by the first, Population III, stars, which in turn reflects how massive those stars were. The key goal is to derive their observational signature, to be probed with upcoming next-generation facilities, such as the James Webb Space Telescope.Astronom
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GRB Cosmology: Probing The Early Universe
Current observations are about to open up a direct observational window into the final frontier of cosmology: the crucial first billion years in cosmic history when the first stars and galaxies formed. Even before the launch of the James Webb Space Telescope, it would be possible to utilize Gamma-Ray Bursts (GRBs) as unique probes of cosmic star formation and the state of the intergalactic medium up to redshifts of the first stars. The ongoing Swift mission might be the first observatory to detect individual Population III stars, provided that massive metal-free stars were able to trigger GRBs. Swift will empirically constrain the redshift at which Population III star formation was terminated, thus providing crucial input to models of cosmic reionization and metal enrichment.Astronom
Constraining the Statistics of Population III Binaries
We perform a cosmological simulation in order to model the growth and
evolution of Population III (Pop III) stellar systems in a range of host
minihalo environments. A Pop III multiple system forms in each of the ten
minihaloes, and the overall mass function is top-heavy compared to the
currently observed initial mass function in the Milky Way. Using a sink
particle to represent each growing protostar, we examine the binary
characteristics of the multiple systems, resolving orbits on scales as small as
20 AU. We find a binary fraction of ~36%, with semi-major axes as large as 3000
AU. The distribution of orbital periods is slightly peaked at < 900 yr, while
the distribution of mass ratios is relatively flat. Of all sink particles
formed within the ten minihaloes, ~50% are lost to mergers with larger sinks,
and ~50% of the remaining sinks are ejected from their star-forming disks. The
large binary fraction may have important implications for Pop III evolution and
nucleosynthesis, as well as the final fate of the first stars.Comment: 16 pages, 14 figures, to appear in MNRA
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